Surface treating appliances such as vacuum cleaners are well known. The majority of vacuum cleaners are either of the “upright” type or of the “cylinder” type (also referred to canister or barrel machines in some countries). An upright vacuum cleaner typically comprises a main body containing dirt and dust separating apparatus, a pair of wheels mounted on the main body for maneuvering the vacuum cleaner over a floor surface to be cleaned, and a cleaner head mounted on the main body. The cleaner head has a downwardly directed suction opening which faces the floor surface. The vacuum cleaner further comprises a motor-driven fan unit for drawing dirt-bearing air through the suction opening. The dirt-bearing air is conveyed to the separating apparatus so that dirt and dust can be separated from the air before the air is expelled to the atmosphere. The separating apparatus can take the form of a filter, a filter bag or, as is known, a cyclonic arrangement.
In use, a user reclines the main body of the vacuum cleaner towards the floor surface, and then sequentially pushes and pulls a handle which is attached to the main body of the cleaner to maneuver the vacuum cleaner over the floor surface. The dirt-bearing air flow drawn through the suction opening by the fan unit is conducted to the separating apparatus by a first air flow duct. When dirt and dust has been separated from the air flow, the air flow is conducted to a clean air outlet by a second air flow duct. One or more filters may be provided between the separating apparatus and the clean air outlet.
An example of an upright vacuum cleaner with improved maneuverability is shown in EP 1 526 796. This upright vacuum cleaner comprises a barrel-shaped rolling assembly located at the lower end of the main body for engaging the floor surface to be cleaned, and which rolls relative to the main body for allowing the main body to be rolled over the floor surface using the handle. The rolling assembly is rotatably connected to arms which each extend downwardly from a respective side of the base of the main body. A C-shaped yoke extending about the external periphery of the rolling assembly connects the cleaner head to the main body. Each end of the yoke is pivotably connected to a respective arm of the main body, whereas the cleaner head is connected to the forward, central part of the yoke by a joint which permits the yoke to be rotated relative to the cleaner head. These connections allow the main body to be rotated about its longitudinal axis, in the manner of a corkscrew, while the cleaner head remains in contact with the floor surface. As a result the cleaner head may be pointed in a new direction as the main body is rotated about its longitudinal axis. As the main body is pushed over the floor surface using the handle, the vacuum cleaner moves forward along the direction in which the cleaner head is pointed, thereby allowing the vacuum cleaner to be smoothly and easily maneuvered over the floor surface.
The main body of the vacuum cleaner houses separating apparatus for separating dirt from a dirt-bearing air flow drawn into the cleaner head. To increase the stability of the vacuum cleaner, and to make efficient use of the space within the rolling assembly, the motor-driven fan unit for drawing dirt-bearing air into the suction opening is located within the rolling assembly.
A number of air ducts convey air through the vacuum cleaner. First and second serially-connected air ducts extend about one side of the yoke and one of the arms of the base to convey a dirt-beating air flow from the cleaner head to the separating apparatus. A third air duct conveys a clean air flow from the separating apparatus to the motor-driven fan unit located within the rolling assembly. This third air duct passes through the outer surface of the rolling assembly, co-axial with the rotational axis of the rolling assembly, and so a bearing arrangement needs to be provided between the third air duct and the rolling assembly to allow relative movement therebetween. The air flow may be exhausted from the rolling assembly through an outlet located between the bearing arrangement and the third air duct, or through a fourth air duct located between the bearing arrangement and the third air duct. This fourth air duct may return the air flow to the main body, which houses a filter for removing fine particulates from the air flow before it is exhausted from the vacuum cleaner.
The provision of ducting around the rolling assembly can restrict the maneuverability of the vacuum cleaner through narrow spaces, for example between items of furniture. WO2008/025956 describes another upright vacuum cleaner in which the first air duct passes through the rolling assembly. In this vacuum cleaner, the yoke is in the form of a curved shell pivotably connected to a pair of arms which each extend downwardly from a respective side of the base of the main body. The rolling assembly comprises a barrel-shaped central roller rotatably mounted to the yoke, and a pair of cap-shaped outer rollers each rotatably attached to a respective side of the yoke. The first air duct passes through the rolling assembly from the cleaner head to the main body such that the first air duct passes over the central roller, and is generally shielded from view when the vacuum cleaner is in an upright position. A second air duct conveys a dirt-bearing air flow from the first air duct to separating apparatus housed in the main body, and a third air duct conveys a cleaner air flow from the separating apparatus to a motor-driven fan unit located within the main body, beneath the separating apparatus. The air flow is exhausted from the vacuum cleaner through an air outlet formed in the main body. While this upright vacuum cleaner has a narrower shape than that described in EP 1 526 796, the height of the main body is increased due to the requirement to house the motor-driven fan unit within the main body. Furthermore, the location of the fan unit in the main body raises the center of gravity of the vacuum cleaner, which can make the vacuum cleaner more difficult to maneuver over the floor surface than the vacuum cleaner described in EP 1 526 796.